1. Field of the Invention
This invention relates to a recording liquid suitable for ink-jet recording by ejecting droplets through orifices of a recording head as well as for recording by use of usual writing tools.
2. Description of the Prior Art
Ink-jet recording generates less noise and permits high speed recording on plain paper without requiring any particular fixing treatment, so that various types of ink-jet systems are investigated energetically.
Recording liquid for use in the ink-jet system is demanded to fulfill the following requirements: (1) its physical properties such as viscosity and surface tension are within proper respective ranges; (2) it does not clog fine orifices for discharging; (3) it gives recording images with clear color and with sufficiently high optical density; and (4) it does not make any change in its physical properties or deposit solid matter during storage. In addition, the following properties are requested: (5) recording can be performed on any of recording media such as paper and the like; (6) it can be fixed on recording media at high rates; (7) it gives images which are excellent in resistance to water, solvent (in particular, alcohol resistance), light, and abrasion and have a high degree of resolution; and (8) it is innocuous to human body.
On the other hand, when used for recording by means of conventional writing tools such as fountain pens, felt pens, and the like, recording liquid is requested to have similar properties as in the case of ink-jet recording, in particular to be excellent in solution stability (the above requirements (2), (4) and such) since the supplement of recording liquid to pen points are accomplished by making use of capillarity. Accordingly, a recording liquid which fulfills the requirements in ink-jet applications can also be used in conventional writing tool applications.
Recording liquid used for ink-jet recording is composed basically of a dye for recording purposes and its solvent. The above noted properties of recording liquid are much affected by properties proper to the ingredient dye and by the solvent composition. It is therefore very important in the art to select a dye and a solvent composition so as to provide the recording liquid with the above properties requested.
The solubility of the ingredient colorant in vehicle materials is of great importance, that is, a sufficient solubility of the colorant in water and also in a water-miscible organic solvent such as a wetting agent is essential for the recording liquid to maintain a good anti-clogging property and a high storage stability.